• on Test & Measurement
  • Published in issue 4/2010 on page 26
About the article


A switch-mode 0–30 V / 3 A bench supply


This power supply is based on an integrated switching regulator to keep the component count within reasonable limits. The functional units of this IC include voltage regulation, switching signal generation, and integrated power switch. This means that only a few external components are necessary.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update
* Adjustable secondary-side switch-mode power supply (buck converter)
* Output voltage 0–30 V (typical) (25 V minimum)
* Adjustable current limiting up to 3 A
* Maximum output power 90 W
* Compact PCB layout
* Switching frequency 52 kHz
* Parts kit available from the Elektor Shop
(default: 250 mW 1%)
R1,R2 = 820Ohm
R3 = 240Ohm
R4,R5 = 560Ohm 1W
R6 = 0.05Ohm 5W (Vishay Dale type LVR05R0500FE73 or 1.73Ohm/m resistance wire, see text)
R7,R8 = 12kOhm
R9 = 47kOhm
R10 = 39kOhm
R11 = 160kOhm
R12,R13 = 1kOhm
R14 = 100Ohm
R15 = 100kOhm
R16 = 10kOhm
P1 = 25kOhm potentiometer, linear
P2 = 250kOhm potentiometer, linear
P3 = 50Ohm trimpot, multiturn, vertical
P4 = 10kOhm trimpot, multiturn, vertical
P5 = 50kOhm trimpot, multiturn, vertical
P6 = 1kOhm trimpot, multiturn, vertical
P7 = 200Ohm trimpot, multiturn, vertical
C1 = 10,000µF 50V radial
C2,C3 = 220µF 63V radial
C4 = 100µF 63V radial
C5 = 2200µF 63V, radial
C6 = 680pF ceramic
C7 = 100nF ceramic
L1 = 330µH 4.5A (muRata Power Solution type 1433445C) or 330 µH 3A (Würth type 744137)
B1 = 800V 6A bridge rectifier (e.g. Vishay type GSIB680)
D1 = 1N5822 (Schottky diode, 40V 3A)
D2,D3 = 1N4007
D4 = zener diode 22V 1W
D5 = zener diode 18V 1W
D6 = 1N4148
D7 = LED, 3mm, red, low current (2mA)
IC1 = LM2576T-ADJ (National Semiconductor) (see text)
IC2 = LM337LZ
IC3 = LM358AN
TR1 = power transformer, secondary 25V 3.2 A (see text)
Heatsink for IC1 (T0-220 <9.9K/W, e.g. Fischer Elektronik type SK129 25,4 STS)
K1,K2 = 2-pin PCB terminal block, lead pitch 5mm
K3 = 6-pin DIL pinheader, lead pitch 2.54mm (0.1’’)
PCB, order code 090786-1
Kit of parts, contains all components except power transformer. Order code 090786-71
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